High-intensity discharge (HID) lighting technology is in some ways similar to that of fluorescent lamp technology. The HID lamps generally have two electrodes at either end in a closely filled gas tube. An arc is established between two electrodes in a gas-filled tube, which causes a metallic gas vapor to produce radiant energy. In fact when sufficient high voltage of 3 KV˜4 KV peak to peak is applied to the electrodes, an arc is formed between them. This high voltage is termed as ignition voltage. If the lamp is hot, this voltage ranges up to 20 KV, which is termed as hot re-strike ignition voltage. Electrons in the arc stream collide with atoms of vaporized metals, shifting the wavelength of this energy into the visible range, thereby producing light without adding any phosphor coating in the inner side of the bulb. In addition, the length of the electrodes is only few inches and the gases in the tube are highly pressurized. The arc generates extremely high temperatures, causing vaporization of metallic elements in the gaseous atmosphere and the release of massive amounts of visible radiant energy. There are three primary types of HID lamps: a mercury vapour lamp, a sodium lamp and a metal halide or a ceramic metal halide. The nomenclature of the above lamps refers to the elements that are added to the gases in the arc stream, which cause each type to have somewhat different colour characteristics and overall lamp efficiency. These lamps are used extensively, as they are efficient and have a high brightness output. Mercury vapour lamp lighting is the oldest HID technology. The mercury vapor lamp produces a bluish light that renders colours poorly. Therefore, most of the mercury vapour lamps have phosphor coating that alters the colour temperature and improves colour rendering to same extent. Although, these are not the most efficient HID lamps, these were often used because of their longer lifetime with respect to the other types of the HID lamps. Concerning sodium lamps, high-pressure sodium sources were developed primarily for their energy efficiency.
Further, mercury and sodium vapours in the ceramic arc tube produce a yellow/orange light with extremely high LPW (Lumen per Watt) performance and exceptionally long service life (up to 40,000 hours). High-pressure sodium lamps render colours poorly, which tends to limit their use to outdoor and industrial applications where high efficacy and long life are priorities. Metal halide lamps or ceramic metal halide lamps are among the most energy efficient sources of white light available today. These lamps feature special chemical compounds known as “halides” that produce light in most regions of the spectrum. They offer high efficacy, excellent colour rendition, long service life, and good lumen maintenance. Because of their advantages, metal halide lamps are used extensively in outdoor applications and in commercial interiors.
The HID lighting system deliver a high brightness output and are typically used in large retail stores, industrial buildings, shopping malls, and studios ceiling lighting. The HID lighting system is most commonly use for parking lots and street lighting. New applications include automotive headlamps; front projection for meeting rooms and rear projection (DLP TV's) are also now using the HID lighting system. The HID systems consist of high pressure sodium (HPS) lighting systems as well as metal halide lighting systems (MH) or advanced ceramic metal halide lighting system (CMH).
The HID lamps have unique electrical characteristics and require a careful and specific control method, so these HID lamps must require a HID ballast circuitry or choke to properly supply the lamps themselves. The HID ballasts are an integral part of high intensity density discharge (HID) lighting system. The HID ballast regulates the flow of electrical current to the HID lamp to maintain its steady operation. The HID lamps require a high voltage for ignition, typically 3 kV to 4 kV, but more than 20 kV if the lamp is hot. Therefore, the HID ballast component should provide the sufficient ignition voltage for the arc generation, which is not provided by these HID ballast. Before ignition, the HID lamp is in open circuit. After the HID lamp ignites, the lamp voltage drops quickly from the open-circuit voltage to a very low value—typically 20 V—due to the low resistance of the HID lamp. If otherwise unimpeded, this characteristic causes the lamp current to increase to a high value; therefore, the HID ballast must limit the lamp current to a safe maximum level, which is not provided by these HID ballast. As the lamp warms up, the current decreases as the voltage and power increase. Eventually, the lamp voltage reaches its nominal value, typically 100 V, and the ballast regulates the power to the correct level.
Many high intensity discharge lighting systems incorporate or are traditionally powered by standard conventional type electro-magnetic HID ballast, which operates with a basic copper core/coil transformer, capacitor for power factor correction and igniter for the ignition. These components simply start and maintain the lamp operating functions.
However, the present electromagnetic ballast exhibits following has disadvantages:    (a) Low efficiency because of internal high KVAR reactive or inductive losses due to copper winding resistance and iron core losses;    (b) Low power factor, High total harmonic distortion (THD);    (c) Are susceptible to incoming voltage fluctuations thereby causing large lamp power and brightness variation;    (d) Have a hard initial start up which degrade the life expectancy of the lamp;    (e) Generally cannot be dimmed;    (f) Physically heavy weight and large size making them difficult to install in aerial situations;    (g) Have many wires to interconnect which complicates their installation;    (h) More noisy with age;    (i) operated at relatively high temperatures;    (j) Can be damaged by power surges; and    (k) Faster aging.
Many of the prior art based intelligent light network management uses a radio frequency (RF) based wireless control technologies for the remote monitor and control of each HID lamp. Here Radio Frequency (RF) modem is integrated within the Electronic Ballast, which uses the radio waves as the communication media. Through the use of mesh (repeater-based) RF networking and new protocols, these technologies are purported to offer the performance of twisted pair solutions but offers very poor robustness against sources of interference, very limited distance operation, mediocre battery performance, and in one case, response times slower than sneaker net. The underlying RF modems used within these control networks are made by, or the technology is sourced from, a common pool of semiconductor manufacturers. The RF technology of the prior art share many common underlying elements and limitations. For example, all of these systems use mesh networking, in which RF-based devices can also operate as repeaters, to compensate for the poor distance of their radio. The strength of an RF signals drops 6 dB for every incremental doubling of open field distance with no impairments or obstacles. The presence of typical building construction materials such as gypsum panels, metal-foil wall paper, aluminum wall braces, and office or factory equipment further reduces RF signal strength. An RF signal drops inside a typical building with obstacles/impairments by about 25 dB for every incremental doubling of distance. None of the RF mesh networks would work in such environment.
Further, the RF signalling is regulated by national governments; all of the RF technology suppliers must share their assigned RF frequency spectrum that's in common with other authorized RF-based devices and systems. The devices that share the 868 MHz (Europe), 915 MHz (United States), 865 MHz (India), 433 Mhz (china) and ISM 2.4 GHz bands that unlicensed, mesh network-based control networks operate on include 802.11 (Wi-Fi) routers and network interfaces, cordless phones, Bluetooth devices, audio and video extenders, closed circuit television transmitters, and other control networking devices. The interference between different wireless devices reduces reliable communication between any two devices. Various RF technologies use different techniques to mitigate interference caused by other devices in their space. For example, 802.11 (Wi-Fi) and Zig-Bee uses Direct Sequence Spread Spectrum (DSSS) to distribute the information over a wider bandwidth, while Bluetooth uses Frequency Hopping Spread Spectrum (FHSS) to randomly move from channel to channel. Cordless phones based on both DSSS and FHSS are available on the market. Interference among multiple DSSS devices operating in adjacent bands poses a problem due to overlapping caused by spectral re-growth of the frequency bands. The net result, compounded by shared use of a limited frequency range, is reduced system performance and reliability. The growing number of RF devices operating within the shared frequency bands is creating virtual RF traffic jams, and a corresponding degradation in reliability. The downside of RF is that it's hard to penetrate metal building materials; the allowable frequency bands are increasingly crowded and therefore, subject to interference; and bidirectional RF devices requires either multiple receivers or repeaters to propagate a reasonable distance.